In 1999, California observes the 150th year of the Gold Rush. Rather than an isolated historical event, it could be argued that the California Gold Rush never really ended, but rather that it was the first chapter in a mass migration unlike any other in history, both in scale and duration.
At the founding of the Missions by Franciscan friars, Alta California was almost an afterthought, with few known natural resources and, most significantly, little water to sustain permanent European settlement. Other than a “harvest of Souls”, and a Spanish decision to establish a foothold against the Russians, the British and others, there was little to attract attention here.
Barely eighty years later, all that changed forever. When mining fever subsided, a series of real estate booms marked California history in the late 19th and early 20th Centuries. The establishment of the transcontinental rail link, the worldwide advertisement for California’s mild climate provided by the movie industry, the development of agriculture in the Central Valley, the hope of a new life during the Great Depression, the mobilization to defend the West Coast and fight in the Pacific during World War II, and the development of aerospace and high technology industries, all contributed to massive, sustained growth in California in the past 150 years.
All this required water. With a firm and growing economic base with which to respond to growing demand, periodic droughts and other water shortages, California has embarked on a series of massive water engineering projects. This has been especially pronounced in southern California in the 20th Century. The Owens Valley Aqueduct was completed to Los Angeles before 1920, using mule teams to haul steel pipe into isolated canyons. An all-gravity aqueduct brilliantly designed by William Mulholland, it was the longest such structure built since the time of the Romans, and the first of California’s water mega-projects. The Colorado River Aqueduct was built in the early days of the post-War boom, and relied on the taming of the River provided by the recently completed Hoover Dam. In the 1960s, the State Water Project brought the rivers of the Sierras’ western slope to southern California. And in the 1990s, after a thirty-year hiatus, several massive water projects are once again underway. Like their predecessors, these projects also represent the cutting edge of geological and hydraulic engineering. After all, only here do coastal cities reach to the driest of deserts in search of water.
The San Diego Association of Geologists (SDAG) is privileged to be able to host a field trip to view several of these remarkable projects, representing different stages of construction. The geologic setting of southern California, as complex as it is, presents varied problems to large and critical engineered structures; this field trip will emphasize engineering measures undertaken to address geologic problems.
This volume presents papers relating to the sites visited on the field trip. The Inland Feeder Tunnel Project will convey State Project water from Lake Silverwood, in the northwest San Bernardino Mountains, to the distribution network in the “Inland Empire”. This project relies on modern tunneling and subterranean navigation equipment to bore through highly deformed rock in the foothills of the San Bernardino Mountains. The Seven Oaks Dam, nearing completion, is a large flood control structure on the Santa Ana River, also at the foot of the San Bernardino Mountains. The design of these two projects was greatly influenced by their proximity to the San Andreas fault zone; thus, recent research into earthquake recurrence and severity along the San Andreas is very relevant to both the engineering of large water projects, and to the reliability of southern California’s water supply. Partly to address this problem, the Eastside Reservoir Project was designed to provide a six-month supply of water to the metropolitan areas. In addition to increasing the regional water storage capacity, the Eastside Reservoir will also supply water to southern California in the event of an earthquake strong enough to disrupt the water conveyance facilities crossing the San Andreas fault. Construction of the Eastside Reservoir, nearing completion, has also yielded an invaluable collection of Pleistocene vertebrate fossils, providing an assemblage that complements the famous Rancho La Brea finds, and establishing southern California as the preeminent locality for late Pleistocene land fossils. Finally, the Olivenhain Reservoir in the San Diego area, just starting construction, will provide water storage for rapidly growing North County.
In addition to the field trip itself, SDAG is pleased to present new research papers discussing regional water resources development. This begins with a look back. An understanding of long-term precipitation trends is critical to planning for the utilization of local sources of water in San Diego and other parts of southern California. Demonstrating that a reliable supply of water was a critical concern from the very beginning, a surprisingly ambitious water system, probably begun in the late 18th Century, was built for Mission San Diego de Alcalá. Groundwater supply is an ongoing concern in San Diego, both in the granitic highlands and along the coastal plain; several papers address these issues. Finally, where groundwater quality is less than ideal, cutting-edge treatment technologies are being used to supply potable water. This volume provides a snapshot of the projects currently underway to supply drinking, irrigation and recreational water resources to a thirsty region.